Mind Your Safety

Entering Outdoor Substations, Part 4 of 8

One time at a 230kV substation, we observed a worker casually coming through the substation with a 10-ft piece of conduit over his shoulder. The distance between the conduit to the lines under which he was walking was perhaps 8 feet. It is very difficult to know how close a worker can inadvertently swing a piece of conduit to high-voltage lines and draw an arc; it is so difficult to find volunteers willing to give this a try... this person, though, was apparently willing.

At the same time, a parallel conduit is going to be a prime target for induction. When I’m doing substation safety courses, I take a 3-ft piece of conduit, clip a multimeter set to millivolts to one end and clip the other end onto a ground point (yes, I’m using my gloves). I do this in a safe place away from lines, but in parallel to the highest lines in the station. As soon as I lift the conduit off the ground, there is an increase in millivolts. As I move the conduit closer to the lines— either vertically or horizontally—there is an immediate millivolt reaction and great practical learning for my students.

No one plans to swing something into overhead lines, so we need to plan for unplanned occurrences, such as being stung by a wasp.

A worker wearing insulated boots can be blinded to induction. I recently learned of an unfortunate accident where a young man lost control of his truck and hit a powerline on a dark night. Realizing he was late, his fiancée went to find him. She saw his vehicle lights off the road in the snow, but she did not realize he had broken the pole and the powerline was down. She chose a path down to the vehicle and, without incident, helped him out. Unfortunately, they took a different path back to the road.

As they struggled through the snow back to the road, they came into the ground-gradient field from the downed powerline, and both were substantially burned.

In a situation like this, there would have been tingle voltages available on the snow that would have increased in intensity as they walked toward the downed line but, as both were wearing rubber winter boots, they were blinded to this warning until the step voltage was high enough to flash over and between them.

Always watch what any other workers are doing. When you see anyone preparing to operate a switch, you need to distance yourself from that equipment. Over the years, many an operator and electrician has inadvertently opened a non-load break switch under load. One of our clients lost a substation because of this: someone started opening a non-load break switch and, when the arcing occurred—rather than quickly close the switch—the frightened worker fell to the ground, covered his head and balled himself up.

The ensuing arcing spread across the top of the conductors, creating fireworks atop the substation, taking both it and the plant it served out of service immediately. Obviously, the worker was not properly trained, which is why we were hired to ensure the other workers were. (A training audit of your workers can prevent instances like this.)

Workers should wear their rubber gloves while switching. An Eastern utility lost a foreman several decades ago when a cable came off a 3-gang switch during switching and landed on the bottom side of the insulator; he was not wearing his gloves and was electrocuted. No one plans an accident, so make sure you plan for safety.

As you enter the control room, you should follow the same safe work practices you would follow in an indoor substation or any electrical room. Until next time, be ready, be careful and be safe.©

Canada Training Group has been providing consulting services to industry since 1980; Dave Smith, the president, can be reached at davesmith@canada-training-group.ca